Binary hydrocarbon insulating liquid, preparation method thereof and application of binary hydrocarbon insulating liquid in oil-immersed transformer

Abstract

The invention discloses binary hydrocarbon insulating liquid, a preparation method and application of the binary hydrocarbon insulating liquid in an oil-immersed transformer, and belongs to the technical field of liquid insulating dielectrics. The binary hydrocarbon insulating liquid is composed of the following components in percentage by volume: 10-30% of short-chain low-branched alkane; the balance is long-chain multi-branched alkane, and the total percentage is 100%; in the short-chain low-branched alkane, the number of carbon atoms of a first main chain is 15-20, the number of first branched chains is 1-2, the first branched chains are methyl and / or ethyl, and the first branched chains are distributed at the end part of the first main chain; in the long-chain multi-branched alkane, the number of carbon atoms of a second main chain is 21-28, the number of second branched chains is 2-6, and the second branched chains are methyl and / or ethyl. The binary hydrocarbon insulating liquid provided by the invention has excellent lightning impulse insulating performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid insulation dielectric, more particularly to a binary hydrocarbon insulation liquid, a preparation method and application in oil-immersed transformers. BACKGROUND

[0002] With the rapid development of ultra-high voltage power grid construction and the continuous improvement of power equipment capacity, oil-immersed power transformers are facing more stringent lightning impulse insulation performance requirements. Lightning impulse insulation performance is a key indicator for measuring the insulation characteristics of insulation liquid under transient high voltage impulse, and is directly related to the safe operation of power equipment under extreme weather conditions such as lightning.

[0003] Although traditional mineral insulation oil has relatively good lightning impulse breakdown voltage, it has poor environmental performance, low biodegradation rate, and long-term pollution to the environment after leakage, which cannot meet the requirements of green power development. In addition, the thermal stability of mineral oil is poor, which can easily age during long-term operation, resulting in gradual degradation of lightning impulse insulation performance.

[0004] In recent years, in order to solve the environmental problem of mineral oil, natural esters and synthetic esters and other bio-based insulation oils have become a research hotspot. However, ester-based insulation oil has a fatal technical defect: the lightning impulse breakdown voltage is significantly lower than that of mineral oil, about 40% to 60% of that of mineral oil. This performance shortcoming seriously restricts the application of ester-based insulation oil in ultra-high voltage and large-capacity power equipment, and becomes a key technical bottleneck hindering its promotion. SUMMARY

[0005] To solve the above problems, the present application provides a binary hydrocarbon insulation liquid, a preparation method and application in oil-immersed transformers. The binary hydrocarbon insulation liquid has excellent lightning impulse insulation performance, and also has obvious advantages in environmental performance, while meeting the requirements of current insulation oil related standards, and has good application prospects in high voltage grade and large-capacity power equipment.

[0006] The first object of the present application is to provide a binary hydrocarbon insulation liquid, which is composed of the following components by volume percentage: Short-chain low-branched alkane: 10% to 30%; the rest is long-chain multi-branched alkane, totaling 100%.

[0007] In the short-chain low-branched alkane, the number of first main chain carbon atoms is 15 to 20, the number of first branch chains is 1 to 2, the first branch chains are methyl and / or ethyl, and the first branch chains are distributed at the end of the first main chain.

[0008] In the long-chain multi-branched alkane, the number of second main chain carbon atoms is 21 to 28, the number of second branch chains is 2 to 6, and the second branch chains are methyl and / or ethyl.

[0009] The volume resistivity of short-chain, low-branched alkanes is 1.3 × 10⁻⁶. 12 The lightning impulse breakdown voltage is 177.29 kV / mm. With the increase in the number of carbon atoms in the first main chain of short-chain, low-branched alkanes, the lightning impulse insulation performance decreases slightly, but the thermal stability and flash point significantly improve. When the first branch is only methyl, the intermolecular spacing is moderate, resulting in excellent lightning impulse insulation performance and good biodegradability. When the first branch is only ethyl, the steric hindrance effect is enhanced, further improving the lightning impulse insulation performance, but the biodegradability decreases slightly. When the first branch is both methyl and ethyl, the various performance indicators tend to be in a coordinated balance.

[0010] In long-chain branched alkanes, the second branch is located at a position at least one carbon atom away from the end of the second main chain. In long-chain branched alkanes where the second branch is irregularly distributed, the volume resistivity is 1.7 × 10⁻⁶. 12 The lightning impulse breakdown voltage is 162.89 kV / mm. With the increase in the number of carbon atoms in the second main chain of long-chain branched alkanes, the molecular viscosity gradually increases, and the thermal stability improves, but the impact insulation performance and biodegradability gradually decrease. When the second branch is only methyl, a moderate steric protective structure is formed, resulting in good thermal stability and a high level of biodegradability. When the second branch is only ethyl, the steric hindrance effect is significant, further improving thermal stability, but the biodegradability decreases. When the second branch is both methyl and ethyl, the overall performance is more stable.

[0011] This invention achieves a unique synergistic effect mechanism at the molecular level by controlling a specific ratio of short-chain, low-branched alkanes to long-chain, multi-branched alkanes, fundamentally solving the technical bottleneck of existing insulating liquids' lightning impact insulation performance. The core of this invention's compounding strategy lies in utilizing the high impact insulation strength of short-chain molecules as the performance foundation, while introducing an appropriate amount of long-chain, multi-branched alkanes to balance and optimize other key performance indicators. This realizes the molecular design concept of compensating for weaknesses with strengths and achieving synergistic effects, resulting in a binary hydrocarbon insulating liquid with a significantly higher lightning impact breakdown voltage than that obtained by using long-chain, multi-branched alkanes alone. Simultaneously, it exhibits significantly better thermal stability, viscosity control, and biodegradability than short-chain molecules alone.

[0012] Compared with existing technologies, the core innovation of this invention lies in the molecular design concept based on the lightning impact insulation mechanism and biodegradation mechanism. The alkane molecules selected in this invention have a straight-chain structure. Compared with the cycloalkanes and aromatic hydrocarbons commonly found in mineral oils, straight-chain alkanes have a simpler structure and better molecular chain flexibility, making them easier for microbial enzyme systems to recognize and degrade. Therefore, the molecular design based on this straight-chain structure gives this invention superior biodegradability compared to traditional mineral oils, with a biodegradation rate of 72.9%–78.7%, far exceeding the 30% of mineral oils. This significantly reduces the risk of environmental pollution and meets the higher environmental performance requirements of green power equipment.

[0013] This invention achieves a balance between environmental performance, high lightning impulse insulation performance, and high volume resistivity by controlling the specific ratio of two types of alkanes with different chain lengths and degrees of branching. This is not achieved in existing mineral oils, ester oils, and their mixtures. This invention directly addresses the application needs of ultra-high voltage and large-capacity power equipment, exhibiting performance parameters superior to existing mineral oils and ester insulating oils. It also possesses high biodegradability, balancing environmental protection and safety. The binary hydrocarbon insulating liquid proposed in this invention, with its high insulation resistance and strong impulse insulation properties, outperforms traditional mineral oils and existing ester insulating oils and mixed insulating oils in terms of lightning impulse voltage resistance, significantly improving the insulation safety and operational reliability of power equipment. Other properties meet the requirements of current insulating oil standards, making it a viable alternative to existing mineral insulating oils for use in high-voltage and large-capacity power equipment such as transformers. It demonstrates good industrial feasibility and promising prospects for widespread application.

[0014] In a preferred embodiment of the present invention, the components are composed of the following volume percentages: 20% to 30% short-chain, low-branched alkanes; the remainder being long-chain, multi-branched alkanes, totaling 100%.

[0015] In a preferred embodiment of the present invention, the short-chain low-branched alkane has 18 carbon atoms in the first main chain and 1 branch.

[0016] In a preferred embodiment of the present invention, the long-chain multi-branched alkane has 23 carbon atoms in the second main chain and 3 branches.

[0017] In a preferred embodiment of the present invention, the structural formula of the short-chain, low-branched alkane is shown below: .

[0018] In a preferred embodiment of the present invention, the structural formula of the long-chain branched alkane is shown below: .

[0019] A second objective of this invention is to provide a method for preparing the aforementioned binary hydrocarbon insulating liquid, comprising the following steps: Short-chain, low-branched alkanes and long-chain, multi-branched alkanes are mixed evenly, filtered, and dried to obtain a binary hydrocarbon insulating liquid.

[0020] A third objective of this invention is to provide the application of the aforementioned binary hydrocarbon insulating liquid in oil-immersed transformers. The performance parameters of the binary hydrocarbon insulating liquid in this invention meet the requirements of IEC 60296 and can be used in environmentally friendly oil-immersed high-voltage transformers.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a binary hydrocarbon insulating liquid comprising the following components: short-chain, low-branched alkanes: 10 vol.%–30 vol.%; long-chain, multi-branched alkanes: 70 vol.%–90 vol.%. This invention achieves a balance between environmental performance, high lightning impulse insulation performance, and high volume resistivity by controlling the specific ratio of two types of hydrocarbon liquids with different chain lengths and degrees of branching. The short-chain, low-branched alkanes have smaller molecular volumes and weaker intermolecular forces, allowing them to rapidly rearrange under the strong electric field of a lightning strike, providing a rapid dissipation channel for the charge. Their low viscosity promotes ion migration and prevents charge accumulation in localized areas. Meanwhile, the long-chain, multi-branched alkanes form a three-dimensional shielding structure, effectively dispersing and homogenizing the electric field distribution, avoiding localized electric field concentration. Simultaneously, the three-dimensional molecular network constructed by their multi-branched structure provides a stable insulating matrix, significantly enhancing the overall dielectric strength. When the short-chain component is controlled within the critical ratio range of 10 vol.% to 30 vol.%, the excellent lightning impact insulation performance of the short-chain molecules can be fully utilized. At the same time, through the dilution and modification of long-chain multi-branched alkanes, better thermal stability, viscosity characteristics and environmental performance can be obtained while maintaining high impact insulation strength.

[0022] Traditional ester-based insulating oils contain polar C=O groups. Under a strong electric field, the lone pair electrons of oxygen atoms migrate to carbon atoms, forming transient dipoles. This increases the risk of charge accumulation and local electric field distortion, resulting in a significant reduction in breakdown voltage. While mineral oils are nonpolar molecules, they lack synergistic design at the molecular level. Relying solely on saturated alkanes with single-chain lengths cannot achieve the optimal match between charge transport and structural stability. Furthermore, their cycloalkanes and aromatic hydrocarbon structures result in poor biodegradability.

[0023] This invention utilizes nonpolar straight-chain alkane molecules to completely eliminate the negative impact of polar groups. Simultaneously, through a double-chain long gradient design and optimized branching structure, methyl / ethyl branches are distributed at the ends of the main chain, with the number of branches controlled to 1-2. This fully leverages the dual advantages of high ionization energy and high impact insulation of short-chain, low-branched alkane molecules. Precise control of the proportions is crucial: when the proportion of short-chain, low-branched alkanes is below 10 vol.%, their excellent impact insulation performance cannot be fully realized, and the overall performance is mainly limited by the lower impact insulation performance of long-chain, multi-branched alkanes; while the impact insulation performance is further improved when the proportion of short-chain, low-branched alkanes exceeds 30 vol.%, it leads to problems such as excessively low viscosity and a decreased flash point, affecting the overall performance in practical applications. Therefore, a proportion of short-chain, low-branched alkanes ranging from 10% to 30% achieves the optimal balance between high impact insulation performance and overall application performance. This invention provides new scientific guidance for the molecular design of high-performance insulating liquids through the synergistic insulation theory of short-chain dominance and long-chain auxiliary properties. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] For ultra-high voltage and large-capacity power equipment, key technical issues to consider when using insulating oil include: the conflict between lightning impulse insulation performance and environmental degradation performance; traditional mineral oils, while having good impulse insulation performance, have an extremely low biodegradability rate of approximately <30%, while bio-based ester oils, although having a high degradation rate, have a significantly lower lightning impulse breakdown voltage; the challenge of balancing electrical properties with flow and heat dissipation performance; high molecular weight components, while providing good insulation strength, can lead to excessively high viscosity, affecting heat dissipation, while low molecular weight components, although having good flowability, may pose a safety hazard due to a low flash point; and the coordination between long-term operational stability and initial high performance, where insulating liquids need to maintain excellent initial electrical properties while ensuring long-term thermal stability and anti-aging properties.

[0026] Furthermore, among the insulating oils disclosed in the prior art, patent CN101198682B proposes an electrical insulating oil formulation containing a base oil component and additives. The base oil is an alkane-based oil, but it does not specify the short-chain / long-chain ratio or the molecular branching structure design. Moreover, patent CN101198682B improves oxidation stability and low-temperature performance by adding antioxidants and other additives, without emphasizing lightning impulse insulation performance. Patent CN119317689A proposes a hydrocarbon component, mainly used for fuels, with performance optimization focusing on viscosity, cloud point, density, etc., without emphasizing lightning impulse insulation performance. None of the above patents consider lightning impulse insulation performance; therefore, the insulating oils designed in the prior art do not meet the application requirements of ultra-high voltage and large-capacity power equipment.

[0027] Current technological gaps are particularly evident in the lack of systematic research on the effects of molecular chain length, branching degree, and branching position on the impact insulation performance of insulating oils. The molecular structure, including chain length, branching degree, and branching position, is directly related to the ionization, electron affinity, and excitation processes of insulating oils, thus affecting their impact insulation performance. Furthermore, the synergistic effects between different components of the same molecular type, i.e., the proportion of physical mixing, also significantly influence performance, yet this has not been fully studied and applied.

[0028] Based on the above technical challenges, this invention selects a method of compounding double-chain long-chain alkane molecules, and conducts polarity design through the following aspects: 1. Regarding the principle of chain length selection, short-chain, low-branched alkanes should choose C... 15 ~C 28 This is because this chain length range can provide sufficient thermal stability and a suitable flash point to meet the safe operation requirements of power equipment. At the same time, its large molecular volume is conducive to the formation of a stable insulating matrix. Although its impact insulation performance is relatively poor when used alone, it can effectively balance other key performance indicators in a compound system.

[0029] 2. In terms of branching degree design principles, short-chain, low-branched alkanes adopt low branching degree to appropriately reduce molecular symmetry while maintaining high ionization energy, avoiding crystallization tendency caused by excessively regular molecular arrangement. At the same time, slight branching helps improve low-temperature fluidity. Long-chain, multi-branched alkanes adopt multi-branching design mainly to disrupt the linear structure of molecules, prevent strong entanglement and aggregation between long-chain, multi-branched alkanes, ensure uniform dispersion in the compound system, and the multi-branched structure is beneficial to increasing the number of attack sites of biodegradable enzymes.

[0030] 3. Key considerations for the selection of branching groups and their positions include: Methyl and / or ethyl are chosen as branching groups because these two alkyl groups have moderate steric hindrance. Methyl is small in size and has little steric hindrance, mainly playing the role of breaking molecular symmetry and providing moderate steric protection. Ethyl is slightly larger in size and can more effectively prevent π-π stacking and van der Waals interactions between molecules. If methyl and ethyl are used in combination, the intermolecular distance and interaction strength can be precisely controlled.

[0031] The choice of placing the first branch of short-chain, low-branched alkanes at the ends of the main chain rather than in the middle is based on considerations of electron transport mechanisms. End branches do not interfere with the conjugated electron transport path of the main chain, maintaining the electrical continuity of the molecule. In contrast, middle branches would cause electron transport blockage and scattering, reducing the molecule's dielectric properties. Furthermore, end branches provide effective steric protection, preventing oxidation and polymerization reactions of the molecular end groups. This carefully designed molecular structure allows short-chain molecules to maintain good chemical stability while providing excellent impact insulation properties, while long-chain, multi-branched alkanes, while ensuring thermal stability and environmental degradability, exhibit good compatibility with short-chain molecules. Ultimately, this achieves a multi-optimized balance of electrical properties, thermal stability, environmental performance, and application applicability.

[0032] The short-chain, low-branched alkanes and long-chain, multi-branched alkanes used in the embodiments of this invention were all purchased from Shanghai Daopu Chemical Co., Ltd. In Examples 1 to 3, the short-chain, low-branched alkanes were designated 2835H, and the long-chain, multi-branched alkanes were designated ICCSYN3. In Example 4, the short-chain, low-branched alkanes were designated 2018H, and in Example 5, the long-chain, multi-branched alkanes were designated ICCSYN4.

[0033] Example 1 This embodiment proposes a binary hydrocarbon insulating liquid with high insulation resistance and strong impact insulation properties, composed of the following components by volume percentage: Short-chain, low-branched alkanes: 30%; Long-chain, multi-branched alkanes: 70%.

[0034] The molecular formula of short-chain, low-branched alkanes is C 19 H 40 .

[0035] The structural formula is as follows: .

[0036] The molecular formula of long-chain multi-branched alkanes is C 25 H 52 .

[0037] The structural formula is as follows: .

[0038] After mixing short-chain, low-branched alkanes and long-chain, multi-branched alkanes evenly according to the above proportions, the mixture is filtered and dried to obtain a binary hydrocarbon insulating liquid. The purpose of filtration and drying is to remove moisture, acidic substances, and impurity particles, reducing the moisture content to below 20 ppm.

[0039] Example 2 This embodiment proposes a binary hydrocarbon insulating liquid with high insulation resistance and strong impact insulation properties, composed of the following components by volume percentage: Short-chain, low-branched alkanes: 20%; Long-chain, multi-branched alkanes: 80%.

[0040] The molecular formula of short-chain, low-branched alkanes is C 19 H 40 .

[0041] The structural formula is as follows: .

[0042] The molecular formula of long-chain multi-branched alkanes is C 25 H 52 .

[0043] The structural formula is as follows: .

[0044] After mixing short-chain, low-branched alkanes and long-chain, multi-branched alkanes evenly according to the above proportions, the mixture is filtered and dried to obtain a binary hydrocarbon insulating liquid. The purpose of filtration and drying is to remove moisture, acidic substances, and impurity particles, reducing the moisture content to below 20 ppm.

[0045] Example 3 This embodiment proposes a binary hydrocarbon insulating liquid with high insulation resistance and strong impact insulation properties, composed of the following components by volume percentage: Short-chain, low-branched alkanes: 10%; Long-chain, multi-branched alkanes: 90%.

[0046] The molecular formula of short-chain, low-branched alkanes is C 19 H 40 .

[0047] The structural formula is as follows: .

[0048] The molecular formula of long-chain multi-branched alkanes is C 25 H 52 .

[0049] The structural formula is as follows: .

[0050] After mixing short-chain, low-branched alkanes and long-chain, multi-branched alkanes evenly according to the above proportions, the mixture is filtered and dried to obtain a binary hydrocarbon insulating liquid. The purpose of filtration and drying is to remove moisture, acidic substances, and impurity particles, reducing the moisture content to below 20 ppm.

[0051] Example 4 This embodiment proposes a binary hydrocarbon insulating liquid with high insulation resistance and strong impact insulation properties, composed of the following components by volume percentage: Short-chain, low-branched alkanes: 10%; Long-chain, multi-branched alkanes: 90%.

[0052] The molecular formula of short-chain, low-branched alkanes is C 17 H 36 .

[0053] The structural formula is as follows: .

[0054] The molecular formula of long-chain multi-branched alkanes is C 25 H 52 .

[0055] The structural formula is as follows: .

[0056] After mixing short-chain, low-branched alkanes and long-chain, multi-branched alkanes evenly according to the above proportions, the mixture is filtered and dried to obtain a binary hydrocarbon insulating liquid. The purpose of filtration and drying is to remove moisture, acidic substances, and impurity particles, reducing the moisture content to below 20 ppm.

[0057] Example 5 This embodiment proposes a binary hydrocarbon insulating liquid with high insulation resistance and strong impact insulation properties, composed of the following components by volume percentage: Short-chain, low-branched alkanes: 10%; Long-chain, multi-branched alkanes: 90%.

[0058] The molecular formula of short-chain, low-branched alkanes is C 19 H 40 .

[0059] The structural formula is as follows: .

[0060] The molecular formula of long-chain multi-branched alkanes is C 28 H 58 .

[0061] The structural formula is as follows: .

[0062] After mixing short-chain, low-branched alkanes and long-chain, multi-branched alkanes evenly according to the above proportions, the mixture is filtered and dried to obtain a binary hydrocarbon insulating liquid. The purpose of filtration and drying is to remove moisture, acidic substances, and impurity particles, reducing the moisture content to below 20 ppm.

[0063] Comparative Example 1 This comparative example presents a binary hydrocarbon insulating liquid, composed of the following components by volume percentage: Short-chain, low-branched alkanes: 40%; Long-chain, multi-branched alkanes: 60%.

[0064] The molecular formula of short-chain, low-branched alkanes is C 19 H 40 .

[0065] The structural formula is as follows: .

[0066] The molecular formula of long-chain multi-branched alkanes is C 25 H 52 .

[0067] The structural formula is as follows: .

[0068] After mixing short-chain, low-branched alkanes and long-chain, multi-branched alkanes evenly according to the above proportions, the mixture is filtered and dried to obtain a binary hydrocarbon insulating liquid. The purpose of filtration and drying is to remove moisture, acidic substances, and impurity particles, reducing the moisture content to below 20 ppm.

[0069] Comparative Example 2 This comparative example presents a binary hydrocarbon insulating liquid, composed of the following components by volume percentage: Short-chain, low-branched alkanes: 80%; Long-chain, multi-branched alkanes: 20%.

[0070] The molecular formula of short-chain, low-branched alkanes is C 19 H 40 .

[0071] The structural formula is as follows: .

[0072] The molecular formula of long-chain multi-branched alkanes is C 25 H 52 .

[0073] The structural formula is as follows: .

[0074] After mixing short-chain, low-branched alkanes and long-chain, multi-branched alkanes evenly according to the above proportions, the mixture is filtered and dried to obtain a binary hydrocarbon insulating liquid. The purpose of filtration and drying is to remove moisture, acidic substances, and impurity particles, reducing the moisture content to below 20 ppm.

[0075] Comparative Example 3 This comparative example presents a binary hydrocarbon insulating liquid, composed of the following components by volume percentage: Short-chain, low-branched alkanes: 90%; Long-chain, multi-branched alkanes: 10%.

[0076] The molecular formula of short-chain, low-branched alkanes is C 19 H 40 .

[0077] The structural formula is as follows: .

[0078] The molecular formula of long-chain multi-branched alkanes is C 25 H 52 .

[0079] The structural formula is as follows: .

[0080] After mixing short-chain, low-branched alkanes and long-chain, multi-branched alkanes evenly according to the above proportions, the mixture is filtered and dried to obtain a binary hydrocarbon insulating liquid. The purpose of filtration and drying is to remove moisture, acidic substances, and impurity particles, reducing the moisture content to below 20 ppm.

[0081] The binary hydrocarbon insulating liquids with high insulation resistance and strong impact insulation properties prepared in Examples 1 to 3 were tested for key properties such as acid value, dielectric loss, flash point, volume resistivity, and lightning impulse breakdown voltage. The results were compared with those of traditional mineral insulating oil, single short-chain low-branched alkanes, single long-chain multi-branched alkanes, and Comparative Examples 1 to 3. The results are shown in Tables 1 and 2. It should be noted that the single short-chain low-branched alkanes and single long-chain multi-branched alkanes have the same structural formula as those in Example 1.

[0082] Table 1 Key performance parameters of binary hydrocarbon insulating liquids prepared in different embodiments

[0083] Table 2 Key performance parameters of different control groups

[0084] Table 3 Key performance parameters of binary hydrocarbon insulating liquids prepared in different comparative proportions

[0085] As shown in Tables 1 and 2, the volume resistivity and lightning impulse voltage of the binary hydrocarbon insulating liquids of Examples 1, 2, and 3 are superior to those of mineral oil, and other performance parameters meet the relevant standards of GB2536-2011. This indicates that the binary hydrocarbon insulating liquid of the present invention has high insulation resistance and strong impulse insulation characteristics, demonstrating significant technical advantages. In particular, the performance indicators of the binary hydrocarbon insulating liquids of Examples 1 and 2 are superior to those of traditional mineral insulating oils. Specifically, compared with 25# naphthenic mineral oil, the binary hydrocarbon insulating liquids of Examples 1 and 2 have lower viscosity, and the pour points of the bio-based environmentally friendly insulating oils of Examples 1 and 2 are 19°C and 17°C lower, respectively, than those of 25# naphthenic mineral oil, indicating safer operation in cold regions. Simultaneously, the flash points are 26.5°C and 30.5°C higher, respectively, than those of 25# naphthenic mineral oil, indicating that the binary hydrocarbon insulating liquid of the present invention has superior high-temperature resistance. Furthermore, the biodegradability of the binary hydrocarbon insulating liquids in Examples 1 and 2 is significantly higher than that of 25# naphthenic mineral oil, indicating that the binary hydrocarbon insulating liquid described in this invention has outstanding environmental performance advantages. The binary hydrocarbon insulating liquid in Example 3, except for a slightly higher kinematic viscosity than 25# naphthenic mineral oil, exhibits superior performance in all other aspects compared to 25# naphthenic mineral oil.

[0086] As shown in Table 3, although Comparative Examples 1 to 3 showed excellent performance in terms of biodegradability, with a biodegradability of 86% to 95%, their lightning impulse breakdown voltage was significantly low, ranging from 170.43 kV / 10mm to 172.45 kV / 10mm, which was far lower than the performance level of Examples 1 to 3, namely 174.86 kV / 10mm to 173.02 kV / 10mm.

[0087] The root cause of this phenomenon lies in the change of molecular-level mechanisms after the ratio deviates from the optimal range: When the volume percentage of short-chain low-branched alkanes exceeds 30%, the volume percentage of short-chain low-branched alkanes in Comparative Example 1 is 40%, the volume percentage of short-chain low-branched alkanes in Comparative Example 2 is 80%, and the volume percentage of short-chain low-branched alkanes in Comparative Example 3 is 90%. Although the high ionization energy characteristics of short-chain low-branched alkanes are more fully utilized and theoretically higher lightning impulse insulation performance should be obtained, an abnormal decline in performance actually occurs. The mechanism of this anomaly lies in the fact that a high proportion of short-chain molecules disrupts the molecular coordination equilibrium of the complex system: First, an excessive amount of short-chain, low-branched alkanes leads to an insufficient proportion of long-chain, multi-branched alkanes in the system, making it impossible to form an effective molecular entanglement network and a three-dimensional shielding structure, resulting in insufficient structural stability under strong electric field impact; Second, the interaction between short-chain, low-branched alkanes is relatively weak, and when they aggregate at high concentrations, they are prone to local rearrangement and phase separation under the action of an electric field, forming microscopic inhomogeneous regions. These inhomogeneous regions become electric field concentration points, which in turn reduce the overall breakdown strength; Third, an excessively high proportion of short-chain, low-branched alkanes will significantly reduce the viscosity and intermolecular cohesion of the system. Although this is beneficial for biodegradation, with a degradation rate of 86% to 95%, under the transient high-stress conditions of lightning impact, the low cohesion makes it difficult for molecules to form an effective stress transfer and energy dissipation mechanism, causing impact energy to accumulate more easily in local areas and trigger breakdown.

[0088] Further mechanistic analysis reveals that the key to achieving good biodegradability rates while maintaining excellent impact insulation performance in Examples 1-3 lies in the precise balance between electrical synergy and degradation synergy achieved by maintaining a volume percentage of short-chain, low-branched alkanes within the range of 10%-30%. In terms of electrical synergy, an appropriate amount of short-chain, low-branched alkanes provides a high ionization energy foundation, while sufficient long-chain, multi-branched alkanes ensure the structural integrity of the molecular network. This synergistic effect forms a dual guarantee mechanism of high ionization energy and stable structure. In terms of degradation synergy, the high degradation activity of short-chain, low-branched alkanes combined with the multi-branched structure of long-chain, multi-branched alkanes ensures sufficient enzyme attack sites while avoiding structural instability caused by excessive degradation. In contrast, Comparative Examples 1-3, due to their unbalanced proportions, may have shown outstanding performance in a single performance indicator, such as a high degradation rate, but they lost multiple synergistic effects and could not maintain stable overall performance in the complex application environment of power equipment. This fully demonstrates the scientific nature of the molecular design principles of this invention and the precise requirements of proportion control.

[0089] Therefore, the binary hydrocarbon insulating liquid with high insulation resistance and strong impact insulation properties provided by this invention can be a good substitute for mineral oil and has good application prospects in high voltage level and large capacity power equipment.

[0090] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0091] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A binary hydrocarbon insulating liquid, characterized in that, It consists of the following components by volume percentage: Short-chain, low-branched alkanes comprise 10%–30%; the remainder are long-chain, multi-branched alkanes, totaling 100%. In short-chain, low-branched alkanes, the number of carbon atoms in the first main chain is 15 to 20, the number of first branches is 1 to 2, the first branch is methyl and / or ethyl, and the first branch is distributed at the end of the first main chain; In long-chain branched alkanes, the number of carbon atoms in the second main chain is 21 to 28, and the number of second branches is 2 to 6, with the second branches being methyl and / or ethyl.

2. The binary hydrocarbon insulating liquid according to claim 1, characterized in that, It consists of the following components by volume percentage: Short-chain, low-branched alkanes comprise 20%–30%; the remainder are long-chain, multi-branched alkanes, totaling 100%.

3. The binary hydrocarbon insulating liquid according to claim 1, characterized in that, In short-chain, low-branched alkanes, the first main chain has 18 carbon atoms and the first branch has 1.

4. The binary hydrocarbon insulating liquid according to claim 1, characterized in that, In long-chain branched alkanes, the second main chain has 23 carbon atoms and the second branch has 3 atoms.

5. The binary hydrocarbon insulating liquid according to claim 1, characterized in that, The structural formulas of short-chain, low-branched alkanes are shown below: 。 6. The binary hydrocarbon insulating liquid according to claim 1, characterized in that, The structural formulas of long-chain branched alkanes are shown below: 。 7. A method for preparing a binary hydrocarbon insulating liquid according to any one of claims 1 to 6, characterized in that, Includes the following steps: Short-chain, low-branched alkanes and long-chain, multi-branched alkanes are mixed evenly, filtered, and dried to obtain a binary hydrocarbon insulating liquid.

8. The application of the binary hydrocarbon insulating liquid according to any one of claims 1 to 6 in an oil-immersed transformer.

Images